1. Technical Field
The present invention relates in general to wireless communications devices and in particular to power systems in wireless communications devices.
2. Description of the Related Art
With wireless communications devices, one of two power supply methodologies, pulse width modulation (PWM) and pulse frequency modulation (PFM), can be implemented. Each methodology has different advantages and disadvantages associated with various device operating modes. The main advantage of PWM is that the switching frequency is constant and can be chosen to avoid interference or generally designed for low electromagnetic interference (EMI). The main disadvantage of PWM is the switching efficiency decreases as the load current decreases. Thus, at light load, PWM efficiency is poor. On the other hand, PFM provides better efficiency at low to moderate load currents, as the switching frequency is adjusted in response to the load current. The frequency of operation and corresponding EMI that may interfere with radio frequency (RF) circuit operation, however, is not predictable. As the number of band/mode combinations in a single communication device increases, the PFM mode increasingly compromises performance in some operating conditions.